Ubiquitous roaming support for real-time traffic, such as interactive VoIP, streaming, and the non-real-time data transfer of FTP and e-mail in an access independent manner, is becoming increasingly important. For example, the evolution of the mobility protocols of Mobile IPv4 (MIPv4) and Mobile IPv6 (MIPv6) has made it easier to support ubiquitous roaming. Carriers in the wireless Internet have different mobility capabilities, and mobile clients may also have a variety of mobility capabilities. For example, some operators or carriers may support mobile assisted mobility protocol, such as MIPv6 and Client Mobile IPv6 (CMIPv6), while others may support network assisted mobile protocol, such as Proxy Mobile IPv6 (PMIPv6). In some cases, often the mobile assisted mobility protocols, a mobile node or mobile client may be equipped with a mobility stack, and the mobile node may use an application layer mobility protocol in certain situations.
In a typical roaming environment, two domains can belong to two separate carriers with different mobility support and security and authentication procedures. Accordingly, a mobile node in the Next Generation Wireless Networks may be subjected to roaming that may involve different kinds of movement scenarios. These movement types can be confined to home domain or visited domain. When the mobile node is away from home and is in the visited domain, the mobile node is defined to be in roaming mode. When in the roaming mode, the mobile node can move between two sub-networks that may belong to the same carrier domain, or it can move from one carrier domain to another carrier domain. Any mobile node in roaming scenario may be subjected to several degrees of heterogeneity, such as types of mobility being supported in the network elements and in the mobile node's stack, the type of application supported in the mobile node and type of movement both in the local domain or in the visited domain that might involve changing bearer manager. Also, while in the visited domain, avoiding exposure of a subscriber's permanent IP address in the visited carrier networks is important to maintain security.
Several existing standards bodies are attempting to define the core network architecture for next generation wireless networks. Third Generation Partnership Project (3GPP) defined an IP Multimedia Subsystem (IMS) architecture, and 3GPP2 defined the Multimedia Domain (MMD) architecture. Recently, Advances to IMS (A-IMS) architecture, which enhances existing IMS and MMD networks, has been proposed to support a variety of services such as Session Initiation Protocol (SIP)-based and non-SIP-based applications. SIP-based applications are typically set up by SIP and provide services such as VoIP. On the other hand, non-SIP-based applications provide services such as IPTV and FTP without using SIP. Similarly, International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is working on defining the Next Generation Network (NGN) under the premises of a Global Standards Initiative, i.e. NGN-GSI. All these architectures include heterogeneous access networks, such as CDMA, WiMAX, and 802.11 technologies, and include support for roaming.
At present, however, the inventors know of no flexible framework that can support seamless mobility between networks with different mobility support.
The following abbreviations are used throughout.    3GPP: Third Generation Partnership Project    AAA: Authentication, Authorization and Accounting    AGW: Access GateWays    AN: Access Network    AS: Application Servers    CDMA: Code Division Multiple Access    CMIPv6: Client Mobile IPv6    CN: Correspondent Node    DAD: Duplicate Address Detection    DHCP: Dynamic Host Configuration Protocol    FTP: File Transfer Protocol    GGSN: Gateway GPRS Support Node    GSM: Global System for Mobile communications    HA: Home Agent    hHoA: Home Address of node in home domain    I-CSCF: Interrogating Call Session Control Function    IETF: Internet Engineering Task Force    IMS: IP Multimedia Subsystem    IMS/MMD—combination of IMS and MMD    IPTV: Internet Protocol TeleVision    ITU-T: International Telecommunication Union Telecommunication Standardization Sector    LCP: Link Control Protocol    LMA: Local Mobility Anchor    LTE: Long Term Evolution    MAG: Mobile Access Gateway    MIPv4: Mobile IPv4    MIPv6: Mobile IPv6    MMD: Multimedia Domain    MN: Mobile Node    NAI: Network Access Identifier    NGN: Next Generation Network    NGN-GSI: Next Generation Network-Global Standards Initiative    PCF: Packet Control Function    P-CSCF—Proxy Call Session Control Function    PDSN—Packet Data Serving Node    PMA: Proxy Mobile Agents    PMIPv6: Proxy Mobile IPv6    PPP: Point to Point Protocol    SAE: System Architecture Evolution    S-CSCF—Serving Call Session Control Function    SDP: Session Description Protocol    SIP: Session Initiation Protocol    URI: Universal Resource Identifier    vHoA: Home Address of node in visited domain    VoIP: Voice over IP    WiMAX: IEEE 802.16 wireless specification